National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS66 KPQR 200338
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
837 PM PDT SUN MAY 19 2013

.SYNOPSIS...MILD LATE SPRING WEATHER CONTINUES THROUGH MON. THEN BIG
CHANGES AS A STRONG COLD FRONT SWEEPS ACROSS THE REGION TUE. THIS
WILL BRING MUCH COOLER AND UNSETTLED WEATHER THAT WILL LINGER THROUGH
THEN END OF THE WEEK.
&&

.SHORT TERM...ONSHORE FLOW TURNING A BIT MORE NORTHERLY THIS EVENING.
THIS ALLOWING FOR LARGE AREAS OF CLEARING. NOT MUCH CHANGE OVERNIGHT
AS WILL SEE MOSTLY CLEAR TO PARTLY CLOUDY SKIES.

VERY PLEASANT DAY ON MON...AS HIGH PRES OVER THE REGION BUILDS. AIR
MASS WARMS IN RESPONSE TO THE HIGH...WITH 850 MB TEMPS RUNNING ABOUT
5 TO 8 DEG C ABOVE THOSE ON SUNDAY. WITH PLENTY OF SUNSHINE...THIS
PUTS MONDAY AFTERNOON TEMPS WELL INTO THE 70S FOR INTERIOR...BUT
STAYING COOLER ALONG THE COAST WITH LOWER 60S.

ALL EYES STARTING SHIFTING FURTHER WEST LATER MON AND MON NIGHT...AS
A DEVELOPING LOW THAT IS NOW NEAR 140W AND 47N WILL DRAW CLOSER.
PLENTY OF COLD AIR BEHIND THE FRONT WILL BRING MAJOR CHANGES FOR THE
PAC NW. THE COLD FRONT WILL PUSH ACROSS WESTERN OREGON TUE
MORNING...WITH DRAMATICALLY CHANGE IN TEMPERATURES AND SNOW LEVELS.
SNOW LEVELS WILL START NEAR 8000 FEET AHEAD OF THE FRONT TUE
MORNING...BUT DROP STEADILY IN THE AFTERNOON AND EVENING...DOWN  TO
NEAR 3000 FEET BY LATE TUE EVENING.

WITH SUCH A COLD AND UNSETTLED AIR MASS...ALONG WITH LOW FREEZING
LEVELS...HEAVIER SHOWERS WILL COME WITH SMALL HAIL. THERE IS ALSO A
POSSIBILITY FOR THUNDERSTORMS...DEPENDING ON THE EXACT TRACK OF THE
COLD POOL ALOFT. SOME MODEST DIRECTIONAL SHEAR WED MAY AID THE
THUNDERSTORM DEVELOPMENT...BUT AGAIN THIS DEPENDS ON THE TIMING OF
INDIVIDUAL SHORTWAVES ROTATING AROUND THE BROADER UPPER LEVEL LOW.
WILL HOLD OFF ON ADDING THUNDER MENTION FOR NOW SINCE THERE IS STILL
A LOT OF UNCERTAINTY AS TO HOW THESE EXACTLY THESE ELEMENTS WILL MIX.

.LONG TERM...WEDNESDAY EVENING THROUGH SUNDAY...A LINGERING CLOSED
LOW PRESSURE SYSTEM WILL KEEP THE AREA SHOWERY AND COOL THROUGH THE
WEEK. WITH THE COLD NATURE OF THE LOW...EXPECT SNOW DOWN TO PASS
LEVEL IN THE CASCADES WEDNESDAY NIGHT....WITH SNOW LEVELS RISING
ABOVE THE PASSES THURSDAY AFTERNOON. MODELS HAVE COME INTO BETTER
AGREEMENT FOR THE LONG TERM AND TAKE THE LOW NORTHEAST ON
SATURDAY...WITH A FEW SHOWERS POSSIBLE AS MOISTURE WRAPS AROUND THE
WEST SIDE OF THE LOW. AT THIS TIME SUNDAY LOOKS DRY BUT
CLOUDY...WITH MODEL DISCREPANCIES EMERGING IN REGARD TO THE NEXT
SYSTEM THAT MAY IMPACT THE AREA LATE SUNDAY. BURGESS
&&

.AVIATION...HIGH PRESSURE WILL CONTINUE TO STRENGTHEN OVERNIGHT
INTO MONDAY ALLOWING VFR CONDITIONS TO PREVAIL FOR THE NEXT 24 HRS.
SCT CLOUDS AROUND 5 K WILL CONTINUE TO DECREASE THIS EVENING. SOME
LIGHT RAIN EARLIER THIS MORNING IN THE CENTRAL WILLAMETTE VALLEY MAY
PROVIDE ENOUGH MOISTURE TO ALLOW A PATCHY MVFR STRATUS DECK TO FORM
LATE TONIGHT...BUT CLEARING SHOULD OCCUR QUICKLY MONDAY MORNING. MID
AND HIGH CLOUDS WILL MOVE INTO THE AREA ON MONDAY AHEAD OF THE NEXT
SYSTEM. TODD

KPDX AND APPROACHES...VFR CONDITIONS THROUGH THE NEXT 24 HRS.
&&

.MARINE...HIGH PRES OVER THE NE PAC WILL CONTINUE TO BUILD OVERNIGHT
WITH N TO NW WINDS. THE LOW END SMALL CRAFT ADVISORY FOR WINDS OVER
THE CENTRAL OREGON COASTAL WATERS WILL CONTINUE AS PRESSURE
GRADIENTS HOLD THROUGH MONDAY...ALLOWING GUSTS TO 25 KT FROM CAPE
FOULWEATHER SOUTH. A FEW GUSTS 20-25 KT ARE POSSIBLE OVER THE
NORTHERN WATERS...BUT OVERALL WINDS SHOULD STAY BELOW CRITERIA. SEAS
HOLDING AT 4 TO 6 FT THROUGH TUE...THOUGH MAY GET BIT CHOPPY WITH
BRISK NW WINDS AT TIMES...MAINLY S OF CASCADE HEAD.

MODELS HAVE BEEN SUGGESTING A LARGE AREA OF 10 TO 13 FT SWELL
ARRIVING BY MID WEEK. WE HAVE SEEN THIS SOLUTION FOR A FEW RUNS NOW
SO CONFIDENCE IS GROWING. TODD
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT MONDAY FOR
     COASTAL WATERS FROM CASCADE HEAD TO FLORENCE OUT 60 NM.

&&

$$

MORE WEATHER INFORMATION ONLINE AT...
HTTP://WEATHER.GOV/PORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM
THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA.